Randomly sets ringer volume to 0? Randomly set to silent?Support

I missed a call the other day because I didn't hear my phone. Then I caught a call because I happened to have the phone on the desk next to me and I saw the screen come on and saw the incoming call, but it wasn't ringing. After the call I checked and sound was ON. I checked volume, and the volume sliders for ringer and media were both all the way to the left (0 volume). I didn't set them that way, I know that. And this isn't the first time it's happened.

And just now when I went to look at my phone to see what the media slider was called (couldn't remember at the moment) it said my phone was set to silent!